This invention relates to electronic devices, and more particularly to a packaged power semiconductor device with a metal back plate that is electrically isolated from the terminals of the device.
Electronic semiconductor device technology continues to rapidly advance, producing devices that achieve heretofore unattainable operating speeds, packing density, and high-temperature compatibility. This last characteristic, high-temperature compatibility, is one of more important features. High-temperature environments as well as high-power and high frequency applications are becoming increasingly important. The ability of electronics to withstand high-temperature environments such as gas-turbines, automotive engine compartments, materials handling and fabrication equipment, and aircraft subsystems makes possible many historically impractical electronic applications for these environments.
Many such high-power, high-temperature electronics applications inherently limit the ability to dissipate heat and power generated by the electronics. Thermal and power management as well as environmental protection of the electronics are therefore handled entirely by the electronics packaging. As a result, typical high-performance packaging criteria include mechanical strength, high thermal conductivity, close matching of device and package thermal expansion coefficients, low dielectric constant for accommodation of high frequency devices, and environmental protection, such as hermetic sealing.
In designing such packages, thermal management is importantxe2x80x94especially at high power generation levels which increase the amount of heat created. Heat decreases the performance and operating life of the transistor. Moreover, heat generated at the collector-base junction can create a temperature buildup which may eventually cause the device to short-circuit.
The power device may be mounted on a thermally conductive pad which acts as a heat sink and dissipates the heat generated by the power device. In order to prevent electrical losses, however, the thermally conductive pad must also be electrically insulating. Hence, a thermally conducting, electrically insulating material, e.g., beryllia (beryllium oxidexe2x80x94BeO) and alumina (aluminum oxide), is used for the mounting pad.
The invention provides a packaged power semiconductor device having electrical isolation between the potential of a die inside the package and a metal back side of the package. In one embodiment, a power device compatible with an SOT 227 package standard includes a substrate including a first conductive layer, a second dielectric layer, and a third conductive layer. The first conductive layer is bonded to the second dielectric layer, and the second dielectric layer is bonded to the third conductive layer. The first and third conductive layers are electrically isolated from each other. The first conductive layer has been patterned to provide at least first and second conductive blocks. A semiconductor die is bonded to the first block of the first conductive layer of the substrate. A terminal lead is coupled to the second block of the first conductive layer of the substrate.
A further understanding of the nature and advantages of the present invention may be realized by reference to the remaining portions of the specification and the drawings.